implement the activity system

src/main/java/emu/grasscutter/data/excels/ActivityData.java

@@ -0,0 +1,34 @@
+package emu.grasscutter.data.excels;
+
+import emu.grasscutter.data.GameData;
+import emu.grasscutter.data.GameResource;
+import emu.grasscutter.data.ResourceType;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.experimental.FieldDefaults;
+
+import java.util.List;
+import java.util.Objects;
+
+@ResourceType(name = "NewActivityExcelConfigData.json", loadPriority = ResourceType.LoadPriority.LOW)
+@Getter
+@FieldDefaults(level = AccessLevel.PRIVATE)
+public class ActivityData extends GameResource {
+    int activityId;
+    String activityType;
+    List<Integer> condGroupId;
+    List<Integer> watcherId;
+    List<ActivityWatcherData> watcherDataList;
+
+    @Override
+    public int getId() {
+        return this.activityId;
+    }
+    @Override
+    public void onLoad() {
+        this.watcherDataList = watcherId.stream().map(item -> GameData.getActivityWatcherDataMap().get(item.intValue()))
+            .filter(Objects::nonNull)
+            .toList();
+    }
+
+}